I have reports from one user of our software with the exact same issue with macOS 26.4.1 We call [NSSound play] on a background thread in our app since ~ 2012. Maybe it should now be called on main thread ? However we have not had reports from other users, so I have asked them if they are using a different Audio Output to the Mac Built-in output. As maybe that is the difference. I have attached the crash log. crash.txt